The P7-1 protein of southern rice black-streaked dwarf virus, a fijivirus, induces the formation of tubular structures in insect cells.

Southern rice black-streaked dwarf virus (SRBSDV), an insect- and plant-infecting reovirus of the genus Fijivirus, induced the formation of virus-containing tubules in infected plant and insect vector cells. Expression of the nonstructural protein P7-1 of SRBSDV in insect cells by a recombinant baculovirus resulted in the formation of tubules with dimensions and appearance similar to those found in SRBSDV-infected cells. These tubules protruded from the cell surface, supporting the hypothesis that the P7-1 protein contains two putative transmembrane domains that are necessary for the formation of tubules. Furthermore, the self-interaction of SRBSDV P7-1 protein indicates that this protein has the capacity to form homodimers or oligomers to assemble the proposed helical symmetry structure of tubules. Taken together, our results indicate that SRBSDV P7-1 has the intrinsic ability of self-interaction to form tubules growing from the cell surface in the absence of other viral proteins.